1. Field of the Invention
This invention relates to a method for producing silicone polyethers.
2. Description of the Related Art
DE 31 33 869 C1 (U.S. Pat. No. 4,417,068 A) describes generally the production of silicone polyethers from hydrosiloxanes and alkenyl polyethers in a noble metal catalyzed hydrosilylation reaction. The examples show the influence of catalyst quantity and catalyst structure on the conversion of the SiH groups. The SiH conversion achievable per unit time for a given type of catalyst can only be significantly increased through appreciably higher noble metal concentrations, which is costly and therefore disadvantageous.
A fundamental problem with the production of silicone polyethers is low miscibility of the polymeric feedstocks, which generally results in the reaction mixture being initially biphasic and the production first proceeding very sluggishly.
As is known from U.S. Pat. No. 5,869,727, this disadvantage can be eliminated by adding volatile solvents which can be redistilled off again on completion of the synthesis. The advantage of faster reaction kinetics comes at the cost of a longer product workup and a poorer space-time yield.